Similar machines for the production of ground meat or fish patties etc. are known. According to CH-A No. 506 252 an appliance to form products is equipped with a hopper to hold a supply of the plastic food material, an adjustable mold near the hopper which has a mold opening and which is connected by a channel and a feeding unit in the form of a ram in this channel. The ram is stopped as it travels towards the mold in order to maintain a certain pressure on the product until the mold is moved away from the feed opening. Afterwards the ram can be moved back again to begin the next filling procedure.
Due to changes in the surroundings, especially the temperature of the product, as well as its consistency, the pressure in the product can vary quite considerably so that in one instance too much product is pressed into the mold and the patty is blown after molding, or in other instance the mold is only partially filled.
According to CH-A No. 506 332, a system was built into the same machine, which drives the feeding movement of the ram depending on the pressure of the material in the mold plate opening. Consequently, the desired consistency of the product to be molded can be regulated so that the patties being produced are all of uniform density even when the physical features of the product and/or the feeding speed should alter.
Both these units and other known machines have a piston moving to and fro and a so-called ram to press the ground meat through a fill slot in a mold. It has been proved that gas present in the meat, namely air, can cause a change in the tissue fibres of the meat while being molded, because meat is more permeable than fat so that more fat can be found on one side of the patties. Moreover, the ground meat is pressed against one wall and must flow in a different direction to that of the power vector. This can cause the meat to be torn and it then tastes different than originally intended.